1. Field of the Invention
The present invention relates to an oil cooler for an automobile, in particular to an oil cooler for an automatic transmission used fixedly on its housing by means of stud bolts.
2. Description of the Prior Art
Two kinds of oil coolers for the automatic transmission are known. The configuration of one kind of an oil cooler is such that, as shown on the left side in FIG. 5, tank 15 for radiator 13 connected to engine 11 contains oil cooler 17. The configuration of the other kind of the oil cooler is such that as shown on the right side in FIG. 5, oil cooler 21 is fixed on the housing for automatic transmission 19.
For example, a catalog for "4000S, 4000CS and Coupe GT" manufactured by Audi discloses an oil cooler fixed on the housing for an automatic transmission.
FIGS. 6 and 7 show the oil cooler of this type for the automatic transmission. The oil cooler is characterized by oil inflow stud bolt 25 that carries oil from automatic transmission 19 and by oil outflow stud bolt 27 that feeds oil to automatic transmission 19, the two bolts penetrating at given interval P a water tank which contains a rectangular core made of a plurality of stacked plates.
Stud bolts 25 and 27 permit core 23 to be fixed on housing 29 for automatic transmission 19.
In these Figures, a number of 33 stands for a cooling water inflow tube and a number of 35 for a cooling water outflow tube.
In the oil cooler of the prior art for the automatic transmission, oil inflow stud bolt 25 and oil outflow stud bolt 27 placed on the longitudinal center line of core 23 at given interval P are used to fix core 23 on housing 29 for automatic transmission 19. Thus, it is not easy to circulate oil fully outside both the studs of core 23. This makes it difficult to obtain high thermal exchange efficiency.
A possible means for solving such problem is to widen the interval between oil inflow stud bolt 25 and oil outflow stud bolt 27. However, the means is a deus ex machina, because it is difficult to fix core 23 made of aluminum firmly and securely on the housing for automatic transmission 19 owing to a pressure problem. Further, another problem is brought about that core 23 arranged near the water inlet and outlet lends itself to the undesirable distribution of inflow water.